In the prior art, various types of conveyors have been proposed for material handling. One type of a conveyor uses a combination of an endless belt and a series of idler rolls for belt support. This type of conveyor is used in many types of material handling, including both bulk materials and articles such as baggage and packages. When conveying bulk materials, the idlers may be configured to form a troughed idler conveyor in order to keep the bulk material on the belt during its travel. For items such as baggage and packaging, the conveyor belt can be relatively flat.
Conveyor systems employing idler rolls are not without their disadvantages since they can be quite expensive and high in maintenance. These systems are also noisy and require substantial support structures given the large number of idlers which must be used to support the conveyor belt. Conveyors employing idlers also have a high power consumption due to the mass of the idlers and their friction component.
In an effort to eliminate the use of idler rolls and their drawbacks, belt conveyors have been developed which are supported by air rather than a plurality of idlers. U.S. Pat. No. 3,734,271 to Dolgolenko et al. and U.S. Pat. No. 4,984,681 to Jonkers exemplify conveyor systems using air for conveyor support.
Referring now to FIG. 1, an exemplary air supported conveyor is designated by the reference numeral 10 and includes a conveyor frame 1 supporting a plenum chamber 3. A blower 5 draws air into the plenum chamber 3 and forces it through an orifice 7.
The plenum 3 has a troughed-shaped surface 8 which, with the cushion of air supplied by the blower 5, forms a support for the conveyor belt 9. The conveyor belt 9 follows the contour of the trough-shaped surface 8. Bulk material 11 is shown retained by the conveyor belt 9 for conveying from one location to another. FIG. 1 also illustrates a return conveyor 13 wherein the belt 9 is supported by a plurality of idler rolls 15.
The trough-shaped surface 8 serves as a belt alignment means or guide. With the trough-shape, the bulk material tends to migrate towards the longitudinal axis of the conveyor belt 9, thereby keeping the belt 9 within the trough during belt travel.
Air supported conveyors are not without their own disadvantages. Due to the trough-shaped belt, these types of conveyors are not very adaptable for conveying certain types of articles, e.g., baggage or packaging, that are better suited to travel on a flat conveyor. In addition, even though the conveyor 10 uses an air supported system for the conveying of the bulk material 11, idler rolls are still used in the return conveyor system 13. Thus, the problems noted above with idler rolls are still present in the air supported belt conveyor 10 of FIG. 1.
In view of the disadvantages of prior art conveyor systems as noted above, a need exists to provide an improved conveyor system which overcomes the drawbacks of the prior art. In response to this need, the present invention provides an improved conveyor system and method of article conveying which uses an air supported conveyor belt and a unique belt edge guide system which enables conveying articles on a generally flat belt at high speeds.